Study of impregnating epoxy resins for high field NMR superconducting magnets

NMR magnet coils are usually quite long, thick, and tightly wound with thin superconducting wires. The successful vacuum/pressure impregnation of such kind of coils demands the use of epoxy resins with superior properties such as low viscosity, long pot life, and high cracking resistance etc. In order to find the most appropriate impregnating epoxy resin for the fabrication of high-field NMR magnet coils, the authors have studied several promising epoxy resins by viscosity, thermal shock, bonding/de-bonding measurements. The results of these measurements are presented. Model coils have been vacuum/pressure impregnated with selected epoxy resins and analyzed with scanning electronic microscope (SEM). It was found that among all of the studied epoxy resins the CTD-101K epoxy resin is most suitable for impregnation of coils. The test results of the model NbTi superconducting coil show that coils potted with CTD-101K do not quench until critical current of the superconductor is reached. This epoxy and the impregnation technique have been successfully applied to the first 400 MHz/89 mm actively shielded high resolution NMR magnet developed at Houston Advanced Research Center